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Help. Clutch/ Flywheel vibration problems

NewGuy

Active member
Joined
Aug 30, 2002
Messages
33
Location
Diamond Bar, CA, USA
Corvette
1996 LT4 Collectors Edition
Just had a centerforce clutch and pressure plate put in my 1996 LT4 by a very reputable and long established performance shop. Now find out they do not have much experience on LT4's.

Horrible vibration from drive line now. They checked around and some chevy dealers said never resurface a LT4 flywheel. (which they did). They then called a Corvette specialty shop who said no problem if the shop doing the resurfacing has a special jig that was made for this flywheel. The shop they used for resurfacing does have that jig and it is the same shop the Corvette specialist said he uses.

Questions: Do you or do you not resurface a LT4 flywheel? If not, what do you do? Do you just purchase a new one from GM?

If so, is there any special engine/flywheel balancing procedure that needs to happen?

Any ideas out there? Of course, could have gotten a bad clutch or pressure plate but how do you tell?

FYI, balance the driveshaft and replaced U joints. Vibration happens standing in neutral, rolling, clutch in or out so think that eliminates anything after the tranny.

Please send suggestions. Thanks:mad :mad
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
I thought all the ZF six flywheels where basically the same dual mass design. I am not aware of a difference on the LT4, unless they found some way to make it lighter.

I do know that the G.M. manual says never resurface those. They want you to replace it at about $800. I resurfaced the one in our 89 ZF six with no known problems afterwards. We sold the car about a year after I changed the clutch, and it was as smooth as glass.

There was not specific index point on the last couple that I have seen. In other words, you could put the pressure plate on anyway you wanted, there were no obvious balance marks.

Is it possible that you simply have a defective pressure plate? Maybe it is coming apart and it is slinging some of the internal parts off base?

I can tell you from experience that if you get rid of the dual mass and go with the single mass like I did in my 90 six speed, the instant ability for the engine to rev is awesome! However, the noise when in neutral and clutch out sounds like a rod is loose in the engine.

Even if a dual mass goes bad, I don't think it can throw you out of balance, as the center hub that moves is solid, the outer ring is balanced. It moves around all the time when you are driving anyway.

Anychance a plug wire came loose and the car is just missing on one cylinder? That would make it aweful rough feeling.

Keep us posted, This is a real mystery right now.
 
Joined
Jun 20, 2002
Messages
2,509
Location
Tallahassee, FL
Corvette
none right now :(
I understand you are not supposed to re-surface the flywheel... they also have problems with coming apart... My bet is on the flywheel being bad, from the shop doing something to mess it up.
 

NewGuy

Active member
Joined
Aug 30, 2002
Messages
33
Location
Diamond Bar, CA, USA
Corvette
1996 LT4 Collectors Edition
Latest Update:

Every GM dealer says do not resurface the flywheel. Every Corvette shop said no problem. Seems there was a special jig made awhile back to facilitate resurfacing.

Somehow, I got the last Centerforce clutch/pressure plate in the U.S. (really). Lots of shops say they are great, lots say they are terrible. Made calls to Corvette specialists from New York to Georgia to California. Multiple suggestions and here is what has been done so far:

Centerforce Technical said cannot be a problem with their clutch. (what a surprise) For whatever reason, my flywheel does not have the yellow paint dab on it to line the clutch up with. So, the shop did what Centerforce suggested: put the car in the air, drop the trans, put the clutch in and run the engine. Try all six possilbe positions and go for the one that seems to have the least vibrations. No, I could not believe it either but the shop did it just to see the result. Another big surprise is the shop that did the resurfacing of the flywheel claim they could not have caused an out of balance situation. Guess this just kinda happened all by itself or maybe the Corvette Gods are mad because I also love my BMW.

After assembly, test drove it and although the vibration is less, it is still there.

The only thing we know is that something is out of balance: The shop that did the flywheel resurface could have mounted it incorrectly when doing their job, the clutch is out of balance or the pressure plate is out of balance or, all three are a little out and the combination is causing the major vibration.

New plan: This is a high performance shop that works on many high end cars. Just happen to be rebuilding a LT4 and have a new crank, flywheel and McCloud clutch/pressure plate ready for this engine. They are going to put my flywheel on this crank and determine the amount of out-of-balance (the dual mass flywheels are balanced to the particular engine). Once they get this for a baseline, they are going to bolt the centerforce to it and determine if it is out of balance. They will also be able to measure the run-out of my flywheel on this setup. The theory is that we will find out which component is the culprit.

Worst case scenerio is that we go with a new flywheel and another clutch/pressure plate from another manufacture.

As long as the bell housing is being taken apart for the third time, purchased a new clutch slave cylinder cause I would kick myself if I had to replace it in a few months. Afterall, this car does have 89,000 miles on it.

It has been three weeks now and, you know, C4's look almost as good up in the air as on the ground.
 

NewGuy

Active member
Joined
Aug 30, 2002
Messages
33
Location
Diamond Bar, CA, USA
Corvette
1996 LT4 Collectors Edition
Finally got the car running as it should. Warning to everyone: Do not resurface the dual mass flywheel even if the shop says they do it all of the time. Mine was ruined. Ended up putting in a single mass flywheel. Now vibration free but you do have that gear clatter while at a stop and when taking off in 1st. But the good thing is that there is a noticible improvement in response with the single mass flywheel.
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
NewGuy said:
Finally got the car running as it should. Warning to everyone: Do not resurface the dual mass flywheel even if the shop says they do it all of the time. Mine was ruined. Ended up putting in a single mass flywheel. Now vibration free but you do have that gear clatter while at a stop and when taking off in 1st. But the good thing is that there is a noticible improvement in response with the single mass flywheel.

Hmm, that is what I did to my 90. I used the RAM 900 series clutch. I HATE THE CLUTCH. I should have put a more stock profile/composition disc in there. The pressure plate is a new ZF style, and then the single mass flywheel.

The noise is pretty strong after she warms up and I sit next to a big caddi or something in traffic. You can hear the gear clang bouncing off the walls and cars next to it in traffic.

On a performance note however, it is quick, smooth, and the clutch bites like a mother lover when it is released.
 
Joined
Aug 23, 2002
Messages
290
Location
Michigan
Corvette
96' LT4
Hey Chris.......just curious .....if they ruined the dual mass..........why didn't he (New Guy) make them just replace it.............seems that once in a while gm knows what they are talkin' about when they say not to use a dremel on the flywheel.........
 

NewGuy

Active member
Joined
Aug 30, 2002
Messages
33
Location
Diamond Bar, CA, USA
Corvette
1996 LT4 Collectors Edition
Yes, wrote a pretty strong letter to the shop and expect something but doubt will see full satisfaction. As usual, everyone pointing the finger at the other. All in all, a disapointing experience but somehow it will work out.
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
I would think that having the warnining in writing in the manual would be a pretty strong argument to request they provide some compensation.

BTW, I destroyed my clutch last night at the speed way. More on that later. I have to figure out how to get the car on off the trailer and what to do next.:r
 

NewGuy

Active member
Joined
Aug 30, 2002
Messages
33
Location
Diamond Bar, CA, USA
Corvette
1996 LT4 Collectors Edition
Chris,

When you went to a solid mass flywheel, did you notice a siginificant rise in heat in the passenger compartment from the engine and tranny?

Thought it might be my imagination but maybe the rubber between the two plates on a dual mass acts as an insulator.

Getting pretty frustrated: Last night looked under the car again and saw the composite rear spring is delaminating! There goes another 300 plus rack time to R&R. Afraid to drive it this way. Looks like if it breaks, there goes my rear suspension.
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Hang in there, it will get better.

No, I have not noticed a rise in temps, just noise at idle with the clutch pedal let out.
 

larryfs

Well-known member
Joined
Aug 7, 2002
Messages
101
Location
long island
I just brought a 96 LT4. only 20,000 miles. It has that noise in neutral with the clutch out. I thought it was the throwout bearing??? could it be a previous owner put in a single mass flywheel????

how could I tell which flywheel I have and is it stock.

I didn't plan on pulling it apart to replace the throwout bearing, but now I have to wonder if the flywheel is stock???

any suggestions on how to tell what I have it there...
thx
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
I don't think there is any way to determine which one you have without removing the whole trans.

The stock one makes noise, but the single mass makes much much much more noise.

The noise is a common complaint of six speed owners. I would guess yours is stock with that few of miles.
 
S

SJ LT-4

Guest
I just had my flywheel machined and have no problems. I paid for a brand new one two years ago ($975.00). I just had some engine work done this year, and they pulled the flywheel. The shop I took it to before charged me for a new one, and then put the old one back in. I always ask to see the old parts, now.
 

NewGuy

Active member
Joined
Aug 30, 2002
Messages
33
Location
Diamond Bar, CA, USA
Corvette
1996 LT4 Collectors Edition
From what I found out and this is through communicating with over a dozen shops, they can be resurfaced if the shop doing it has a special jig for it and they are careful.

GM clearly states not to do it. Most Corvette shops said they do have it done. A few Corvette shops said they had a bad experience and will never do it again.

The shop that did mine was the same shop that does resurfacing for two Corvette specialty repair shops in the area. Mine just went bad. Nobody wanted to take the blame and now I have a $1200 claim in on them.

Guess the only answer is you are taking your chances.
 

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